You think that Sheila shot herself once, and then June came over to her, dripped blood on Sheila's arm, and then Sheila lifted the rifle, shot June, and then shot herself again? June would have fallen on top of Sheila in that case.
I've always thought that the first shot had been done by someone struggling to retrieve the gun from Sheila,that it hadn't been done by Sheila herself. It hadn't been a contact shot and it had also hit the jaw-bone. Not somewhere ( the jawbone ) you'd aim for if you were taking your own life. The second,suicide shot was a contact one.
It's not impossible for Sheila to have been lying down as she took a final shot to her mother who,if she'd been struggling to stand,would have been hurled back at the door rather than her falling on top of Sheila,thus slumping as she went down.
We don't know the extent of June's injuries between 4am and 6am to judge if she'd been able to fight off Sheila,or the actual time of the shot that finally killed her. It's obvious that both women struggled,with similar fingernail indentations on June, Neville too, as well as fingermarks around June's throat.
I reckon it had been June at the window possibly trying to summon help,hence the drips on the carpet there,though I wouldn't know where Sheila would have been at that time,or who switched lights on and off and opened and closed curtains.
Without any times of death it's difficult to say who'd been alive at whatever time